Living polymerizations, i.e., polymerizations that proceed in the absence of termination and chain transfer are a most desirable objective of the synthetic chemist. Living polymerizations yield polymers with well defined structures, controlled molecular weight, controlled molecular weight distributions (Mw/Mn) and controlled end functionalities.
In the last decade considerable accomplishments have been made in living carbocationic polymerizations to achieve molecular weight and Mw/Mn control. Some advances have also been made in the synthesis of block copolymers by sequential monomer addition. In copending U.S. Ser. No. 07/730,363, filed Jul. 15, 1991, now abandoned, this technique was used for the preparation of polystyrene-polyisobutylene-polystyrene triblock copolymer thermoplastic elastomers. With many monomer pairs, however, such as isobutylene-paramethylstyrene or vinyl ethers (A. V. Lubin and J. P. Kennedy, J.Polym. Sci., Polym. Chem., 31, 2825, 1993) or .alpha.-methylstyrene (Y. Tsunogea and J. P. Kenedy, J. Polym. Sci., Polym. Chem., 32, 403 1994), a mixture of homo- and/or di- and tri-block copolymers was obtained. The clean synthesis of diblock or triblock copolymers without homopolymer and/or diblock contamination by sequential monomer addition can only be accomplished when the second monomer can be effectively initiated from the living ends. Success also remains limited in the synthesis of functional polymers by in situ functionalization of the living end. For example, only chloro- and allyl-functionalized polyisobutylenes, and chloro-functionalized styrenes could be obtained. This invention provides a method to functionalize the polyolefin chain end, as well as vehicle to produce block copolymers without significant homopolymer contamination.